Print hammer assembly

ABSTRACT

A print hammer assembly is provided for a high speed impact printer wherein a pivoted armature is utilized with a print hammer mounted thereon for initial unitary pivotal motion during which kinetic energy is imparted to the hammer and a terminal period during which the armature is stopped and the print hammer is guided through an over traveled print stroke by a parallel spring mounting that also biases the hammer away from a print condition and toward engagement with the armature.

United States Patent 1191 Carlson et al.

PRINT HAMMER ASSEMBLY inventors: John A. Carlson; William G.

Kempke; Jess J. Sehweihs; Marschelle M. G. Syverson; Larry D. Zolnosky, all of Rochester, Minn.

International Business Machines Corporation, Armonk, NY.

Filed: Feb. 4, 1971 7 Appl. No.: 112,525

Assignee:

u.s. c1. 101/93 c, 197/49 Int. Cl B4lj 9/36 Field 61 Search 101/93 (3, 287, 297

References Cited UNITED STATES PATENTS 8/1964 Wright 101/93 C 4/1965 Antonucci... 101193 C 8/1966 Russo 101/93 C 1451 July 31, 1973 3,301,177 1/1967 Shepard 101/93 C 3,468,246 9/1969 Lee et a1 101/93 c 3,504,623 4/1970 Staller 101/93 c 3,507,214 4/1970 Anderson 101/93 0 Primary Examiner-Robert E. Pulfrey Assistant Examiner-E. M. Coven Aztorneyl-lanifin & Jancin and Robert W. Lahtinen [57] ABSTRACT A print hammer assembly is provided for a high speed impact printer wherein a pivoted armature is utilized with a print hammer mounted thereon for initial unitary pivotal motion during which kinetic energy is imparted to the hammer and a terminal period during which the armature is stopped and the print hammer is guided through an over traveled print stroke by a parallel spring mounting that also biases the hammer away from a print condition and toward engagement with the armature.

4 Claims, 4 Drawing Figures PATENIEU 3. 749.008

sum 1 0F 2 WWW/0R5 JOHN A. CARLSON WILLIAM G. KEMPKE JESS J. SCHWEIHS CHELLE M.G SYVERSON Y D ZOLNOSKY PAIENIEU JUL 3 1 I973 sum 2 or 2 PRINT HAMMER ASSEMBLY BACKGROUND OF THE INVENTION This invention pertains to impact printers in more particularly to high speed print hammer assemblies therefore.

The present invention is directed to an economical, unitized, electro magnetic print hammer assembly for a high speed printer using continuously traveling print characters. This concept rather than using a pivoted print hammer and push rod uses a pivotal armature with a print hammer mounted thereon by parallel springs that additionally provide guidance and biasing.

Previously hammers mounted on parallel springs were tied to ground, while in the structure herein the springs are attached to the pivoting armature. The parallel springs are mounted to preload the hammer against a rigid unitary cushion of the armature and provide for unitary initial pivotal motion of armature and hammer, thereby imparting a discrete kinetic energy to the hammer. When the hammer assembly magnet is pulsed the armature moves to a sealing position against the magnet poles whereupon the hammer continues to travel, guided by the leaf springs and the preload biasing force, to effect the impact print operation.

Upon impact the hammer rebounds to return to engagement with the armature. The energization of the hammer assembly magnet having terminated as the armature seals, the armature is initiating a return to the home position which is assisted by the rebounding hammer. This action also tends to damp the rebound of the hammer, decreasing the settling time and preventing a possible second stroke of the hammer that would induce the unwanted shadow printing.

It is an object of this invention to provide a simplified a high speed print hammer assembly readily adapted to high density packaging. It is a further object of the invention to provide a high speed impact printing hammer with a short dwell for application and cooperation with a continuously moving set of print characters. It is also an object of the invention to provide a hammer assembly wherein the hammer upon rebounding following impact has the kinetic energy promptly damped out to avoid shadow printing and reduce the setting time.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section of an impact printer unit showing a side elevation of the print hammer assembly of this invention.

FIG. 2 is a side elevation of the print hammer assembly of FIG. 1 with portions shown in a section taken along the plane of the surface of the magnet core.

FIG. 3 is a partial isometric view of the armature assembly portion of the print hammer assembly of FIG.

FIG. 4 is a partial planned view of the impact printer of FIG. 1.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2, print hammer assembly presents a core 11 with a leg 12 about which is wound a coil 13 that is surrounded with a molded plastic encapsulation M. The encapsulation M is also provided with a recess 35 which receives armature return spring 16. Molded about a forward portion of core 11 is a yoke 13. A. pair of holes 20 cooperate to positively position the yoke 13 and core It with respect to one another by permitting a positive capture of the core by the plastic material of the yoke 18 during the plastic molding operation. A vertical opening of yoke 18 receives a set screw 2!. which may be advanced or retracted to vary the air gap between the armature portion 22 and the pole faces 23 of the magnet core 11.

Yoke 13 has a longitudinal slotted opening 25 through which is received armature assembly 27. The armature is assembled to the yoke 13 about a pivot pin 29 which is pressed into armature aperture 38 to effect retention by an interference fit. The end portions of pin 29 are joumaled in yoke apertures 23. The mounting spring 31, in the form of a resilient rod, is secured in a recess in core 1 ii and projects upward at a slight forward angle as seen in the unassembled condition of FIG. 2.

Armature assembly 27, as seen in FIGS. 2 and 3, has a magietically permeable metal armature portion 22 and a metal hammer 30. The armature assembly 27 is molded to simultaneously capture armature portion 22 and hammer 30 as inserts. The pair of parallel leaf springs 32 are formed of the plastic material and contain aligned longitudinally extending fiber filler mate rial for reinforcement and fatigue resistance. The plastic preload insert 33 has a rearward portion 34 received and adhesively bonded in a slotted opening 35 and a forward portion 36 received in the slotted opening 37 in the hammer 30. Preload insert 33 causes hammer 30 to be downwardly offset thereby preloading hammer 30 against the insert end portion 36.

As also seen in FIG. 4 a series of hammer assemblies 10 are mounted on a printer frame 40 with two opposed rows of hammer assemblies 10 confronting one another with offset center lines permitting the print hammers 30 to be interdigitated along a common print line. Each hammer assembly 10 is secured to the printer frame 410 through a cylindrical opening 41 in which the mounting spring 31 is received. Withdrawal of the mounting spring wire 31 is prevented by a leaf spring element 43 which is clamped against the spring wire by a bar 4d. An upper comb 46 mounted on printer frame 40 presents slotted openings 47 in which projections 48 on yokes 113 are received and laterally confined and a lower comb 50 presents projections that extend transversely about and confine the plastic encapsulated rear hammer assembly portion 14. The spring wire 31 being at an angle in the unassembled condition (FIG. 2), when assembled to frame 40 causes the hammer assembly forward portion to be biased upward into engagement with the flight time adjusting screw 52 which is threaded through an insert sleeve 53 mounted in frame cylindrical opening 54.

The air gap adjusting screw 21 is adjusted to cause the armature seal time to be equal to the pulse on time during which the magnet is energized. The one degree of freedom afforded hammer assembly 10 is adjusted by movement of flight time adjusting screw 52 to provide the desired over travel of print hammer 30, following sealing of armature portion 22 against pole faces 23, to oppress document 53 and ribbon 59 against the type character 60 which is to be printed.

Type characters 60 are carried by a series of type slugs 611 that are attached to a timing belt 62 and ribbon to move continuously past the printer common print line. The type slugs move along and are supported on a rigid surface 63 and are transversely and vertically confined by the housing 65.

in operation, the magnet coil 13 is pulsed causing the armature portion 22 to seal against the magnet poles 23. Hammer 30 biased against the preload insert 33 by the displacement of the parallel support springs 32 formed as an interval part of armature assembly 27 initially moves in unison with the remainder of the armature assembly. Upon sealing, the armature portion 22 against poles 23, the kinetic energy initially imparted to hammer 30 causes the hammer to over travel through the clearance provided between preload insert forward terminal end 36 and hammer slot 37, against the biasing and restoring force exerted by the parallel support spring portions 32. Upon impact hammer 30 rebounds while simultaneously hammer assembly 27, no longer attracted by the core magnet is initiating a return to the home position. Hammer 30 rebounding assists the return of armature assembly 27 which action also damps the hammer motion in cooperation with the biasing action of springs 43 to prevent a second unwanted print stroke.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a high speed printer, a print hammer assembly comprising:

a pivotably mounted armature assembly of unitary construction including a rigid armature portion, a print hammer having a recessed propelling surface, resilient mounting means including a pair of substantially parallel leaf spring elements each connected at one end thereof to said rigid armature portion and at the opposite end to said print hammer, a preload insert extending from and forming a part of said rigid armature portion and engaging the recessed propelling surface of said print hammer in a lost motion connection;

biasing means engaging said armature assembly for urging said armature assembly in a non-printing pivotal direction;

electromagnetic actuating means positioned for selectively pivoting said armature assembly in a printing pivotal direction;

stop means for limiting motion of said armature assembly in said printing pivotal direction, said stop means being positioned to interrupt pivoting of said armature'assembly in said printing pivotal direction before said print hammer effects printing engagement, whereby upon energizing said electromagnetic actuating means, said armature assembly is pivoted in said printing pivotal direction against the force of said biasing means to a position of engagement with said stop means and thereafter said print hammer, enabled by said lost motion connection, over-travels in a printing direction to effect a print cycle.

2. The high speed printer of claim 1 wherein said armature assembly rigid armature portion, resilient mounting means and print hammer form portions of a single molded part including a plastic matrix.

3. The high speed printer of claim 2 wherein said lost motion connection comprises a recess in said print hammer intermediate said leaf spring elements, and said preload insert extends into said recess and normally engages a recess wall portion facing in a nonprinting pivotal direction to displace said print hammer against the biasing force of said leaf spring elements to provide positive initial movement in a printing direction and to permit said print hammer to move in a printing direction out of engagement with said preload insert against the biasing force of said resilient mounting means.

4. The high speed printer of claim 3 wherein said resilient mounting means leaf spring elements are form ed of a plastic matrix filled with longitudinally aligned fibers. 

1. In a high speed printer, a print hammer assembly comprising: a pivotably mounted armature assembly of unitary construction including a rigid armature portion, a print hammer having a recessed propelling surface, resilient mounting means including a pair of substantially parallel leaf spring elements each connected at one end thereof to said rigid armature portion and at the opposite end to said print hammer, a preload insert extending from and forming a part of said rigid armature portion and engaging the recessed propelling surface of said print hammer in a lost motion connection; biasing means engaging said armature assembly for urging said armature assembly in a non-printing pivotal direction; electromagnetic actuating means positioned for selectively pivoting said armature assembly in a printing pivotal direction; stop means for limiting motion of said armature assembly in said printing pivotal direction, said stop means being positioned to interrupt pivoting of said armature assembly in said printing pivotal direction before said print hammer effects printing engagement, whereby upon energizing said electromagnetic actuating means, said armature assembly is pivoted in said printing pivotal direction against the force of said biasing means to a position of engagement with said stop means and thereafter said print hammer, enabled by said lost motion connection, over-travels in a printing direction to effect a print cycle.
 2. The high speed printer of claim 1 wherein said armature assembly rigid armature portion, resilient mounting means and print hammer form portions of a single molded part including a plastic matrix.
 3. The high speed printer of claim 2 wherein said lost motion connection comprises a recess in said print hammer intermediate said leaf spring elements, and said preload insert extends into said recess and normally engages a recess wall portion facing in a non-printing pivotal direction to displace said print hammer against the biasing force of said leaf spring elements to provide positive initial movement in a printing direction and to permit said print hammer to move in a printing direction out of engagement with said preload insert against the biasing force of said resilient mounting means.
 4. The high speed printer of claim 3 wherein said resilient mounting means leaf spring elements are formed of a plastic matrix filled with longitudinally aligned fibers. 